[Pce] Urgent issue with draft-ietf-pce-stateful-pce : PCE advising PCC about no path

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Hi WG, and draft authors,

We still have an urgent interoperability issue to solve with draft-ietf-pce-stateful-pce. We currently have no clear semantic for the PCE to advise the PCC that there is no more path available. This point was already raised through the list but as we need an URGENT resolution of this issue because of implementation timelines, I would like to reactivate the thread.

The situation of no path at PCE side can happen in many situations, and a particular situation will require PCC to tear down an existing path : let's think about two strictly SRLG disjoint LSPs with a working path . Now the transmission topology is changing (rerouting at WDM layer) leading SRLG disjointness not being fitted anymore and PCE cannot find anymore disjoint path, it must advise one PCC to tear down the path because it is no more disjoint (strict disjointness required).
We do not have any clear semantic today and some implementations are using empty ERO for this purpose in PCUpdate but the PCC does not recognize it as a valid no path significance.

This subject is critical and I would like that we can achieve a consensus asap on the target solution so then vendors can align implementations.
This thread is focusing on the PCE -> PCC way, but having a semantic of reporting a no path is also necessary in PCC->PCE way through PCRpt, at least to ACK a PCupdate.

One of the previous discussion on the list talked about the possibility to use NO-PATH object which already has this semantic for PCReq/PCRep but as already mentioned we need to assess impact on existing implementations, so vendor feedback (with customer implementations) is highly required. So this is my starting proposal to initiate the discussion.


Best Regards,


[Orange logo]<http://www.orange.com/>

Stephane Litkowski
Network Architect
Orange/SCE/EQUANT/OINIS/NET
Orange Expert Future Networks
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